The details of the returns, confirmed by a senior campaign official, provide the most detailed view yet of his wealthy family’s finances. The disclosure comes after a barrage of pressure to release his returns — which Mr. Romney has never done, even when he was elected governor of Massachusetts.

The disclosure — reported early Tuesday by The Washington Post, The Wall Street Journal and Bloomberg News — showed a vast array of investments, from a recently closed Swiss bank account to holdings in Bermuda and the Cayman Islands, all underscoring the breadth and depth of his wealth, which has become a central issue in his bid for the Republican presidential nomination.

Mr. Romney said last week that his effective tax rate was “about 15 percent,” a figure lower than that of many affluent Americans. But his returns suggested that he paid an effective tax rate of nearly 14 percent.

In addition to his 2010 taxes, Mr. Romney is set to release estimates for his 2011 taxes, which he will file in April. The campaign will report that he will pay $3.2 million in taxes for 2011, for an effective tax rate of 15.4 percent. That is a slightly higher effective rate than he paid the year before, when he paid about $3 million to the Internal Revenue Service.

Mr. Romney, a Mormon, has long said that he had promised to give 10 percent of his income to his church. His tax return shows that over two years he and his wife, Ann, gave $7 million in charitable contributions, including $4.1 million to the Church of Jesus Christ of Latter-day Saints.

“I pay all the taxes that are legally required and not a dollar more,” Mr. Romney said during Monday night’s debate. “I don’t think you want someone as the candidate for president who pays more taxes than he owes.”

Mr. Romney also said that there were “no surprises” in his tax returns. Referring to the fact that nearly all of his income is taxed as capital gains at a 15 percent rate, rather than as earned income at rates of up to 35 percent, Mr. Romney questioned a proposal by Newt Gingrich, the former House speaker, to reduce capital gains taxes to zero.

“Under that plan, I’d have paid no taxes in the last two years,” Mr. Romney said.

The Romneys hold as much as a quarter of a billion dollars in assets, much of it derived from Mr. Romney’s time as founder and partner in Bain Capital, a private equity firm. And in federal financial disclosures Mr. Romney made when he began his presidential campaign he said those assets generated at least $9.6 million in income in 2010 and part of 2011, most of it from capital gains, dividends and interest on their investments.

Questions about Mr. Romney’s wealth have dogged him for weeks as his rivals for the Republican nomination assailed his tenure at Bain Capital and pressed for details about his taxes.

Mr. Romney hesitated repeatedly when asked whether he would release his tax returns, as his father had done when he was running for president several decades ago.

Initially, Mr. Romney said that he had no intention of releasing his tax returns, maintaining that the financial disclosure reports that all federal candidates must provide should suffice.

But the pressure grew stronger when Mr. Romney — apparently in an offhand, unplanned way — acknowledged that he pays about 15 percent in taxes, most of it on dividends and capital gains.

Following that statement, the pressure grew for Mr. Romney to release more information by making his tax returns public. Mr. Gingrich pressed him on the issue in two debates

Details about Mr. Romney’s tax payments, wealth and income will inevitably be compared with similar disclosures already made by Mr. Gingrich, as well the man Mr. Romney and Mr. Gingrich hope to unseat, President Obama.

Mr. Gingrich, who on Saturday won the Republican presidential primary in South Carolina, released his own tax returns last week showing that he and his wife, Callista, had an adjusted gross income of $3,162,424 from their various business ventures in 2010. They paid $994,708 in federal tax, according to the return, for an effective tax rate of 31.7 percent.

Mr. Obama and his wife, Michelle, released their tax returns in April, showing an adjusted gross income of $1,728,096 for 2010 — much of it from sales of his books “Dreams From My Father” and “The Audacity of Hope.” The Obamas paid $453,770 in federal taxes, for an effective tax rate of 26.3 percent.

During the debate, Mr. Romney had predicted that there would be little in his tax returns that would prove to be controversial.

“You’ll see my income, how much taxes I’ve paid, how much I’ve paid to charity,” Mr. Romney added in the debate. “You’ll see how complicated taxes can be. And will there be discussion? Sure. Will it be an article? Yeah. But is it entirely legal and fair? Absolutely. I’m proud of the fact that I pay a lot of taxes.”

But the documents are sure to be a source of ammunition for his Republican rivals and his Democratic critics, who have made his personal wealth an issue as he seeks the nomination of his party.

In a memorandum to reporters on Sunday, Bill Burton, a former deputy press secretary to Mr. Obama, hammered Mr. Romney for his initial unwillingness to release his returns.

“Even though he is worth hundreds of millions of dollars, Romney pays a lower tax rate than many middle class Americans,” said Mr. Burton, who now runs a “super PAC” on behalf of Mr. Obama.

“Romney also has access to complicated legal maneuvers involving offshore accounts and retirement savings that simply are not available to everyday Americans,” Mr. Burton said.

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